1. Field of the Invention
The present invention relates to a disk drive, and in particular, to an airtight recording disk drive including a casing for enclosing a disk and a head with respect to the disk. Such recording disk drive can be represented by a hard disk drive unit (HDD).
2. Description of the Prior Art
The existence of dusts and the like in the casing of an HDD, for example, may disturb the precise read and write operations of a magnetic head in the HDD. In order to avoid this disturbance, the HDD may include a circulation filter within the airtight casing. When a magnetic disk rotates, an air stream occurs at the periphery of the disk in the direction of the rotation. The air stream passes through the circulation filter which may catch dust in the air stream. The circulation filter serves to catch lubricating oil leaking from an actuator for driving the magnetic head, and tiny dust generated from the friction in the driving mechanism.
Still higher recording density is required in HDDs representative of the field of information recording. HDDs are accordingly designed to reduce the pitch of recording tracks. The reduction in the pitch of recording tracks may require further accuracy of the tracking operation of a magnetic head. Accuracy of within .+-.0.2 .mu.m, for example, is in fact required for positioning a magnetic head to a magnetic disk of track pitch of 2.54 .mu.m, namely, of 10000 tracks per inch.
Vibration of the rotating magnetic disk greatly affects the accuracy of the tracking operation. In recent years, over 70% of errors in positioning a magnetic head are supposedly caused by the vibration of disks. Accordingly, it is becoming more important to reduce the vibration of the rotating disks.